Not Applicable.
This invention relates to an eductor-mixer system particularly adapted for the preparation of dispersions, solutions and slurries. More particularly, the eductor-mixer system of this invention is an improvement over the eductor-mixer system disclosed in my prior U.S. Pat. Nos. 4,186, 772 and 3,777,775.
An eductor-mixer system is designed to continuously mix a solute such as paint pigments, fire retardants, liquids and gels, (e.g., a powder, particulate, or other pressure transportable or fluidizable material, a liquid or a gas) and a solvent or working fluid (e.g., a liquid or in some instances a gas) to form a dispersion, slurry, or solution.
The solute inlet of an eductor-mixer system is conventionally connected to the discharge outlet of a fluidized container so that a vacuum generated within the eductor-mixer by the flow of solvent (working fluid) through an internal nozzle cooperates with the fluidized discharge of the powder from the container to positively draw the fluidized solute into the eductor-mixer. Existing state-of-the-art eductor-mixer systems typically include a conical, converging stream of working fluid, as most solutes used with these systems require a relatively large diameter solute tube and conveying line (more than 1.0-1.5 inches) to be transported vacuum pneumatically without clumping or clogging. With such large diameter delivery tubes, a conical nozzle is required to deflect the working fluid stream into a discharge tube small enough in diameter to meet the cross-sectional area criterion for vacuum generation and mixing. Although some solute materials may be vacuum transported in smaller diameter tubes, these smaller diameter solute tubes suffer from accretion of the solute material at the discharge outlet due to small amounts of the working fluid splashing back into the solute tube from turbulence formed at the conical deflector in the discharge tube.
Additionally, traditional eductor-mixer systems are thought to be somewhat burdened by the introduction of an radial component of translational energy into the conical converging jet of working fluid, and hence are not as efficient as theoretically possible in generating the vacuum to positively draws the solute thereinto. Reference may be made to U.S. Pat. Nos. 1,806,287, 2,100,185, 2,310,265, 2,695,265, 2,772,372, 3,166,020, 3,186,769, and to Canadian Pat. No. 790,113, each of which discloses various eductor-mixer systems and air conveying apparatus in the same general field as the present invention.
In many known prior art eductor-mixer systems, the powder supply, even if it is in a fluidized container, is required to be located above the level of the eductor-mixer system because the latter is dependent upon gravity feed of the powder. In the systems shown in the U.S. Pat. Nos. 4,186,772 and 3,777,775, the eductor-mixers are not dependent upon gravity feed because the vacuum within the eductor-mixer is sufficient to positively draw the powder from the container into the eductor-mixer systems, and thus these systems are not dependent upon the relative location of the powder container and the eductor-mixer system.
The eductor-mixer system of the present invention is a significant improvement of the aforementioned eductor-mixer systems and is capable of conveying a greater amount of material and generating a higher vacuum pressure due to an improved nozzle design. Furthermore, it overcomes problems associated with splash-back and clogging of narrow diameter solute tubes commonly associated with the use of conical working fluid jets.
Among the several objects and features of this invention may be noted the provision of an eductor-mixer system particularly well suited for either continuous or batch preparation of dispersions, solutions, or slurries from a fine granular, particulate, or powdered solute, or other pressure transportable or fluidizable material and a working fluid or solvent;
The provision of such an eductor-mixer system which is also capable of mixing gas or vapor solutes with liquid or gaseous working fluids; the provision of such an eductor-mixer system which thoroughly mixes the solute and working fluid;
The provision of such an eductor-mixer system which is self-flushing and which effectively prevents back flow of the working fluid into the solute inlet;
The provision of such an eductor-mixer system which minimizes working fluid flow losses therethrough and which is highly efficient in transferring momentum from the working fluid to the solute and to the resulting dispersion;
The provision of such an eductor-mixer system which minimizes the introduction of a radial component of translational energy to the working fluid stream, maximizing the kinetic energy available to produce a vacuum capable of drawing the solute through the solute tube;
The provision of such an eductor-mixer system which eliminates the need for convergence of the working fluid stream, directing substantially all of the working fluid kinetic energy in a longitudinal manner;
The provision of such an eductor-mixer system which is optimized for use with smaller diameter solute delivery tubes;
The provision of such an eductor-mixer system which substantially eliminates splash-back of the working fluid into the solute delivery tube due to turbulence;
The provision of such an eductor-mixer system in which relatively high vacuum levels may be efficiently generated therewithin so as to positively draw fluidizable material into the eductor-mixer system and so that the relative location of the eductor-mixer system and the fluidizable material supply is much less critical;
The provision of such an eductor-mixer system which reduces undesired turbulence adjacent the location of the fluidizable material supply;
The provision of such an eductor-mixer system in which the radial location of the eductor nozzle is dependent upon the outer diameter of the solute tube, and the cross sectional area of the nozzle is proportional to the cross sectional area of the discharge tube;
The provision of such an eductor-mixer system in which certain parts subject to flow erosion may be readily and inexpensively replaced and may be adjusted relative to one another to compensate for wear so as to lengthen the service life while maintaining the desired flow characteristics through the eductor-mixer;
The provision of such an eductor-mixer system in which certain parts thereof may be readily changed so as to vary the flow rate through the eductor-mixer system within a predetermined range; and
The provision of such an eductor-mixer system which is of relatively simple and rugged construction, which is reliable in operation, which may be retrofitted to existing eductor-mixer systems, and which requires no special training or skill for use.
In general, an eductor-mixer system of this invention comprises an eductor body having a working fluid passage extending therethrough for flow of a pressurized working fluid from one end of the working fluid passage, constituting an inlet end, to the other end of the working fluid passage, constituting a discharge end, the working fluid passage being generally of uniform circular cross-section throughout its length. The body has an opening therein opposite the discharge end of the working fluid passage with the opening being coaxial with the discharge end and being of substantially smaller diameter than the diameter of the working fluid passage. A insert comprising a ring separate from the body, having inside and outside faces, and a central opening therethrough from its inside to its outside face, is removably mounted in place at the discharge end of the working fluid passage coaxial with the discharge end. The central opening in the ring being of substantially smaller diameter than the diameter of the working fluid passage. A cylindrical tube of substantially smaller diameter than the diameter of the working fluid passage extends from outside the body through the opening in the body opposite the discharge end of the working fluid passage and extends forward in the working fluid passage from the inner end of the opening in the body into the central opening in the ring. The tube is open at its end in the central opening in the ring, the open end of the tube constituting a discharge end. The tube is axially adjustable in, and removable from, the opening, and is adapted for connection of its end outside the body to a source of fluent material to be educted and mixed with the working fluid for the flow of the material through the tube and out of the discharge end of the tube. The discharge end of the tube is substantially coplanar with the outside face of the ring. The inner periphery of the ring bounding the central opening in the ring is formed in-part as a entrance extending from the inside face towards the outside face of the ring and convergent in downstream direction from the inside to the outside face of the ring, and in part as a cylindrical nozzle surface extending from the narrowest portion of the entrance to the outside face of the ring. The narrowest portion of the entrance of the ring surrounds and is spaced from the cylindrical exterior surface of the tube a distance which is small relative to the diameter of the outer end of the entrance, the cylindrical nozzle surface thereby providing an annular orifice between the exterior cylindrical surface of the tube and the cylindrical nozzle surface of the ring for delivery of the pressurized working fluid from the passage through the orifice. The pressurized working fluid is delivered in the form of an annular jet. The gap between the exterior cylindrical surface of the tube and the cylindrical nozzle surface of the ring is relatively small and the length of the annular cylindrical orifice is relatively short for rapid acceleration of the working fluid flowing through the orifice to a relatively high linear velocity with low flow losses. Means separate from the ring providing a discharge passage downstream from the ring at the discharge end of the working fluid passage in the body in which the material issuing from the discharge end of the tube and the working fluid cylindrically jetted through the orifice may mix, is removably secured to the body at the discharge end of the working fluid passage in the body. The discharge passage extends outwardly from the ring and has an external diameter at its end at the outside face of the ring larger than the diameter of the cylindrical nozzle surface of the ring, the internal surface of the means lying outward of, and parallel to, the projection of the jet throughout its length.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.